Electric lamp



1926 2 Sheets-Sheet 1 y 931. B. CLAUS ELECTRXC LAMP Filed Feb. 1

B. CLAUS ELECTRIC LAMP May 5, 1931.

, 1926 2 Sheets-Sheet 2 Filed Feb. 16

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Patented May 5, 1931 UNITED STATES BRUNO GLAUS, OF SANGERHAUEEN, GERMANY ELECTRIC LAMP Application filed February 16,

My invention refers to electric lamps more especially of the kind in which a non-conductive substance or a substance of low electric conductivity is heated to incandescence by a separate source of heat. It is an object of my invention to provide a lamp of this kind which is more effective and has a greater lighting power than similar lamps hitherto designed.

As is Well known to those skilled in the art, there are substances having a low electric conductivity or being non-conductors, which when heated are capable of converting a far greater quantity of the heating energy 1 supplied to them into light rays than the filaments of the ordinary incandescent lamps. These substances are known under the name of selective radiating bodies; they comprise some of the alkaline earth metals and their oxids and further the rare earth metals more especially in the combinations devised by Welsbach. Unfortunately all these bodies are non-conductors or can be made to conduct the electric current only with great difficulties, so that it seemed hitherto impossible to utilize these substances and bodies in electric lamps including electric arc lamps, inasmuch as these bodies will quickly be atomized under the action of the electric arc,

In the lamp according to the present invention selective radiating bodies of the kind above mentioned are heated to the highest possible temperature by means of heat energy generated by electric means. These selective radiating bodies are of the highest stability even at very high temperatures and they can therefore be heated to far higher temperatures than the filaments hitherto used in lamps, and if so heated, will emit a considerably greater quantity of the heat in the form of light energy, the more so as the maximum of radiating emission is strongly displaced towards the visible part of the spectrum in proportion as the temperature is increased. For the same reason the consumption of current per candle power is greatly reduced.

According to the present invention the 50 heat energy of an electric source of heat is 1926, Serial No. 88,610, and in Germany March 9, 1925.

directed by suitable means to a more or less distant point in which is disposed a selective radiating substance or body. I The electric source of heat may be of any desired kind and may be formed by a filament or an electric are or by other means. As the means for directing the heat energy of the source of heat onto the selective radiating substance or body, I use in the first line deflecting, reflecting and refracting means such as mirrors, lenses and the like. In using reflecting means such as mirrors I prefer using totally reflecting mirrors which allow utilizing substantially all the heating energy emitted from the source of heat, renouncing to the utilization of the light emitted from the source of heat itself.

In that form of my invention which at the present moment appears to me to be preferable to others I use an ellipsoidal mirror formed for instance by a closed bulb of el lipsoidal form and partly coated with a totally reflecting coating, and in one of the two foci of this mirror I place a highly radiating source of heat, in the other focus a highly selective radiating body. In the case where the relative position of the source of heat and the selective radiating body is such, that this latter is also heated by direct convection of heat, I prefer using a selective radiating body whose mass is smaller or at least does not exceed the mass f the ray emitting body, viz. the source of cat.

In the drawings affixed to this specification and forming part thereof a number of electric lamps embod 11g my invention are illustrated diagrammatically by way of example.

In the drawings Fig. 1 is a lamp having an ellipsoidal bulb and a source of heat and a selective radiating body arranged in the two foci which are disposed in a horizontal plane.

Fig. 2 discloses a lamp which is distin- 95 guished from the one shown in Fig. 1 amongst other points by the fact that the source of heat is arranged verticaly above the selective radiating body.

Fig. 3 illustrates a lamp of ellipsoidal form, the curvature of which is however such that the two foci adjoin each other so that the source of heat and the selective radiating body are placed close together.

Fig. 4 shows a lamp in which the selective radiating body partly surrounds the source of heat.

Fig. 5 illustrates a lamp having two sources of heat combined with a single radiating body.

F 1g. 6 illustrates the case of a lamp havingtwo selective radiating bodies and a separate source of heat associated with each other.

Figs. 7-10 are modifications of the type of lamp illustrated in Fig. 4,

Fig. 11 shows a lamp in which the source of heat is superposed to the selective radiating body and having the reflecting part formed differently from the non-reflecting art.

Fig. 12 is a further modification of the lamp shown in Fig. 11,

Fig. 13 shows a lamp in which the radiating body is heated by the heat emitted from an electric arc.

Fig. 14 shows a lamp belonging to the same type, but in which part of the bulb as well as the selective radiating body can be dismounted.

Fig. 15 illustrates a lamp embodying a lens between the source of heat and the selective radiatingbod Referring fi rst to Fig. 1, a is a closed glass bulb of ellipsoidal form, the longer axis of the ellipsoid extending substantially horizontally. About the upper half of the bulb is coated with a totally reflecting coating a of some suitable kind, which may, however, also be replaced by some other totally reflecting body such as a metal shell. In one focus cf the ellipsoidal mirror thus produced is arranged a filament b of some well known kind which is crowded together by coiling as far as possible and which is supplied with current by leads all. In the other focus is arranged a selective radiating body, for instance a body consisting of one of the mixtures of rare earths indicated by l/Velsbach, this bod being supported by means of wires or the'h'ke in such manner as to be insulated as far as possible against the loss of heat.

If the filament b is heated to incandescence by the electric current, all the heat rays emitted from it will be concentrated by reflection onto the selective radiating body 0 in such manner that the temperature prevailing at the point where the body 0 is arranged, is substantially the same as the temperature of the filament b itself, the losses by radiation being comparatively very small. The selective radiating body being thus heated substantially to the temperature of the filament by reflection, will owing to its very high light emitting capacity emit a far more intense light than the filament 6 serving for crease in candle power per unit of current i consumed.

In lamps of this kind goods results can be obtained with a mirror coating which admits the passage of light rays while reflecting heat rays, and very fine metallic layers are for instance suitable for this purpose.

In the lamp disclosed in Fig. 2 the mirror coating a is disposed on the bulb a symmetrically to the longeraxis of the ellipsoidal mirror, which connects the two foci b and 0. I hereby obtain that the irradiation of the selective radiating body 0 is still more powerful than in the lamp shown in Fig. 1, the rays being reflected by a larger mirror and in consequence the body a will give a higher emission of light without this light emission to the outside being reduced by the larger mirror. On the contrary, in this lamp only a small part of the outside rays emitted by the selective radiating body 0 is screened by the mirror coating and the rays emitted from the body 0 therefore light a greater part of the room. The area lighted can easily be regulated by varying the position of the lower focus and the selective radiating body 0 relative to the edge a of the mirror. With the longer axis extending in vertical direction and a corresponding length of the mirror coating this form is particularly suitable for lamps which are intended to throw the light downwards, as is the case for instance in street lighting. Although in this form the emission of light from the body I) is of no importance, the total light emission is favorably influenced if the selective radiating body is heated as highly as possible,

the emission of light from this body increasmg greatly with each rise in temperature. 7 l

The heat rays emitted from the b0 y 0 into the interior of the bulb collect at the point where the incandescent filament b is arranged so that a predetermined temperature can be maintained at this point with a lower consumption of current.

Under certain circumstances it may be advantageous to reduce the eccentricity of the bulb or envelop a reflecting the heat rays as far as possible, the two foci b and c, as shown for instance in Fig. 3, being disposed in close vicinity. This arrangement offers the ad vantage that the body 0 besides being heated by reflection also receives a great part of the heat generated in the filament 6 without reflection, by direct radiation from the filament, this heat being lost in the arrangements before described. Radiated heat is heat that is not reflected but directly radiated from the filament to the selective body. Furthermore in this lamp the two ray emitting bodies I) and 0 appear to the eye only as a single point. However, an appreciable heating and a corresponding increase of light emission by direct radiation from b to a can occur only if the mass of the selective radi ating body 0 is small as compared to the mass of the heat radiating body I). lVith an ellipsoidal envelop having a smaller eccentricity, the reflected image of the source of heat positioned in one focus will also be reproduced more exactly in the other focus than in ellipsoidal bodies having a very high eccentricity. However, the optimum or reflection is not obtained with a spherical body which has an eccentricity equal to zero.

In the lamp illustrated in Fig. 4, the two foci and the two bodies I) and 0, instead of being juxtaposed are superposed. While in this case a greater part of the light rays emitted from the filament b may be screened by the selective radiating body 0, there still predominates as explained also with reference to Fig. 2, the advanta e of the increase of light emission obtained y an increase of temperature of the body 0.

Another form of the lamp, which has proved very useful, is illustrated in Fig. 5. If it is desired to increase the quantity of rays collecting on the body 0, while it does not appear possible to further enlarge the source of heat 6, I can make use of a plurality of sources of heat I), and b which are arranged in the foci of correspondingly formed reflecting envelops a and a the heat rays of these sources of heat being all collected in the point where the selective radiating body 0 is arranged. In the lamp shown in Fig. 5 this is effected by enclosing within an outer oviform bulb a reflecting body or mirror having substantially the form of twin ellipsoidal bodies, the longer axes of which converge towards a single point which is at the same time the common focus of the two ellipsoids. In this point is arranged the selective radiating body 0, while filaments forming the sources of hert are arranged in the other focus of each ellipsoid.

The lamp shown in Fig. 6 resembles in outer form the lamp illustrated in Fig; 1, however, in this case a filament forming a source of heat and a selective radiating body are arranged in each focus. In this manner each one of the selective bodies 0 and 0 is heated as well by the reflected heat rays of the filament disposed in the other focus as also directly by the heat rays of the filament disposed in the same focus. In this lamp the temperature is further increased at the two foci inasmuch as each filament is also heated by reflection from the other filament. In consequence of this arrangement the selective radiating bodies 0 0 can not only be heated to a higher temperature, but also the heat radiating surface of the filaments b b and the surface of the bodies 0 0 can be enlarged.

These advantages, gained by an increase of surface arise also with other forms of the bulb or envelope (1. They become particularly conspicuous if the eccentricity of the ellipsoid forming the bulb is chosen comparatively small, as shown for instance in Fig. 7, where the two foci are closely adjacent one another. In this case only a single filament b extending over both foci of the ellipsoid can be used without any remarkable loss of rays in such manner that the. total radiation emitted from the filament b is concentrated on the selective radiating body 0.

In the lamp shown in Fig. 8 the eccentricity of the envelop is so small that the foci are again disposed in close vicinity to each other. However, in this case, as shown also in Figs. 6 and 7, the ellipsoidal filament b and if desired also the selective radiating body 0 extend over both foci.

Particular advantages are derived from an arrangement of parts as shown, for instance, in Fig. 9, if it is desired to light the ceiling. In this-case the heating body I) and the heated body 0 are preferably arranged in such manner that the radiating body a is capable of taking up, besides the heat concentrated upon it directly and by reflection, also the heat which is carried upwards by the hot current of gas rising from the filament. To this end the electric filament b which extends from one focus to the other, is partly covered by a cap-shaped selective radiating body 0 which need merely be arranged in theupper focus and which is highly heated by the heat rays reflected by the mirror coating covering the lower half of the bulb, further by direct convection of heat from the filament and further by the hot gas current rising from the filament. In this case the radiation by reflection and in consequence also the mirror coating may even be dispensed with altogether.

It is, however, possible to reduce the eccentricity of the ellipsoid, as shown in Fig. 10, to the point where it becomes equal to zero, the ellipsoidal bulb being replaced b a spherical bulb and the filament I) being isposed in the center and being surrounded as closely as possible by the selective radiating body 0. However, this form is not only disadvantageous in that the expansion of the two bodies should only be small in order to give an approximately exact radiating image, but the radiated image of the filament b will also be reflected onto this very filament instead of being concentrated onto the selective radiating body 0. In observing the path of the rays reflected by the spherical envelop, it will appear that the rays emitted from each point of the source of heat are always reflected correctly towards the center only from a very small part of the spherical envelop, while the greater part of the rays will be lost. For this reason, if it is desired to hea a body disposed in the center of the spherical envelop, such heating can be obtained only in case that the mirror coating is altogether impervious to light rays, while, if ellipsoidal envclops are used, the mirror coating may also be partly pervious to light. Moreover in a spher cal envelop the selective body 0 preferably surrounds the source of heat I; and must be comparatively small as compared to the mass of the source of heat 6, if an ap preciable direct heat transmission shall take place from b to c.

In the lamps before described the envelop it extends beyond the part used for reflection without any substantial change of form. However, this is not a condition and, as shown for instance in Fig. 11, only the part of the envelop which operates the reflection of the heat rays, may have the form of an ellipsoid, while the other part may be shaped as desired in each individual case. In the lamp illustrated in Fig. 11 the ellipsoidal envelop a forming the mirror has the form of an ellipsoid; in the focus of which is arranged the source of heat I), while the bulb a, proper surrounding the selective radiating body 0 has spherical form, the body 0 being carried by one of the two envelops.

As shown in Fig. 12 it may also prove advantageous to always provide a part a of the non-ellipsoidal part of the envelop a with a mirror coating,-if it is desired to hereby influence the light rays emitted from the selective radiating body 0.

A further increase in the temperature of the selective radiating body 0 which is accompanied by a very considerable increase in the quantity of light emitted, is obtained if the incandescent filament forming the source of heat in the lamps above described is replaced by an electric arc the heat rays of which are concentrated upon the selective radiating body. The are can be produced in any suitable manner, for instance by causing two bodies such as high melting metals to be moved away from each other when it is intended to light the lamp. With a sufficiently high voltage the two poles of the arc can be kept at a predetermined distance from each other and if the circuit is closed an arc will be formed between them, more especially if the bulb is filled with certain gases or is partly evacuated. Inasmuch as the heat image of the arc is reproduced with out any appreciable loss at the point where the selective radiating body is arranged, the light emission from this body will be considerably greater if an arc is used instead of an incandescent filament.

Fig. 13 is a diagram of a lamp of this kind in which an are e is formed in one focus of the ellipsoidal mirror (1 which highly heats by reflection the radiating body 0 disposed in the other focus. Inasmuch as it is not necessary that the are be formed in an evacuated or gas-filled space, a lamp of this kind can also be formed with a bulb in two pieces, the spherical part a of the envelop being for instance removable in order to exchange the selective body a or the poles of the are e. The spherical part a, may for instance be connected with the ellipsoidal part a by means of screw thread 9. In an arc lam of this kind no means need be provided for adjusting the poles, as in ordinary arc lamps. On the other hand the efliciency of this lamp is still higher than the highest class of ordinary arc lamp were the poles burn away in an appreciable manner so as to require being replaced. Obviously the arc may replace also the filaments in all the other forms of lamps above described.

The advantage of being able to exchange the selective body 0, when it is worn down, can also be obtained with lamps having their source of heat enclosed. This is shown for instance in Fig. 14, where only the part a of the lamp, in which the electric filament b is arranged, is separated by a partition f, impervious to gases but allowing the passage of heat rays, and which may for instance consist of glass, from that part of the lamp which surrounds the selective radiating body 0. This latter body may in this case even be unprotected but it is preferably surrounded by an envelop a removably mounted on the ellipsoidal part a.

The lamp illustrated in Fig. 15 shows that the present invention is not limited to the use of reflecting ellipsoidal bodies. In order to reproduce the heat image of the source of heat 6 at the point where the selective radiating body a is disposed, the envelop a may either have the form of a reflecting paraboloid or hyperboloid which causes the rays emitted from the focus 6 to be directed either in parallel or diverging onto the partition 7 which is here formed by a condensing lens which concentrates these rays onto the point where the selective body 0 is arranged. However, this is only intended to give an example of the many means by which the heat rays can be collected onto this point.

The novel lamp further ofl'ers an opportunity of using for light emission also such substances or bodies which are bad conductors of the electric current, such as for instance the Nernst filament, which become practically conductive only at a ve high temperature. These bodies are well nown to emit an exceptionally great'quantity of light when heated, but up to this day it appeared impossible to employ them for this purpose inasmuch as it seemed impossible to preheat them sufiiciently to render them conductive. However, if such substances or bodies are arranged in the place of the selective radiating body a in a lamp of the kind above described and are connected with current leads, they can be heated by the rays of the source of heat which are concentrated upon them, to so high a temperature as to be come conductive and to convert the current supplied to them directly into light in a very eflicient manner. In a lam of this kind the sourceof heat I) can be ren ered inoperative by any suitable means, while the lamp is burning.

Obviously the novel lamp can be manufactured for any desired candle power. In some cases, for instance if the source of heat is formed by an arc, it may also prove advantageous to arrange the heating body or the heated body, or both, only near their respective focus in order to thus regulate the temperature of the light emitting body. In these cases the dimensions of the source of heat as well as of the li ht emitting body can be increased and the intensity of the light emitted can be reduced so that in this case the light emitting body has a lower brilliancy.

I wish it to be understood that I do not desire to be limited to the exact details of construction shown and described for obvious modifications will occur to a person skilled in the art.

I claim 1. Electric lamp comprising a selective radiating body, an electric source of heat within said body and means for directing substantially all the heat rays emitted from said source onto said body.

2. Electric lamp comprising a curved, el-

lipsoidal mirror, an electric source of heat in one focus of said mirror and a selective radiating body in the other focus of said mirror.

3. Electric lamp comprising a substantially ellipsoidal mirror, a source of heat in one and a selective radiating body in the other focus of said mirror.

4. Electric lamp comprising a substantially ellipsoidal mirror, a source of heat in one and a selective radiatin body in the other focus of said mirror, the 'stance between the two foci being such that a considerable part of the heat rays emitted from said source reach said body directly.

5. Electric lamp comprising a substantially ellipsoidal mirror, a source of heat in one and a selective radiating body of smaller mass in the other focus of said mirror.

6. Electric lamp comprising an ellipsoidal mirror and a source of heat and a selective radiating body near each focus of said mirror.

7. Electric lamp comprising an ellipsoidal mirror of small eccentrlcit a source of heat extending over both foci 0 said mirror and a selective radiating body near one focus.

8. Electric lamp comprising a selective radiating body, an electric source of heat, a partitlon pervious to heat rays between said body and said source of heat and means for directing substantially all the heat rays emit- I ted from said source onto said body.

In testimony whereof I afiix my signature.

BRUNO CLAUS. 

